A known piston machine, in which the working medium can be conducted through the crankcase would for example be a 2-stroke radial engine. The starting point of the invention was not however the intention of providing an improved internal-combustion engine. The objective was rather to provide an improved working machine which can also be used as engine. A known representative of such a working machine is a reciprocating-piston compressor. It cannot however be operated as working machine without having to make extensive constructional modifications to the overall construction of the compressor. Furthermore, compressors usually operate with valve control. A valve control is prone to wear and due to the masses moved permits only limited speeds of rotation. Furthermore, all known working machines operating with valve control have a constructionally inherent dead space wherever valves or valve plates seal the piston working chamber and are always designed so that they simultaneously act as check valve. The dead or waste space gives poor efficiency because working medium compressed therein always remains in the working chamber, i.e. the latter is never completely emptied. Obviously, this reduces the efficiency.
Reciprocating-piston compressors, which today are used in refrigeration apparatuses, have the disadvantage that great damage is caused if liquid occurs in the refrigerant cycle which gets into, the compressor. Usually, the liquid action damages the valve plates. To avoid this disadvantage and further disadvantages the practice is now to use plate compressors, i.e. compressors operating only by the displacement principle. These also have however disadvantages, i.e. greater wear at the discs due to strong area pressure between discs and housing inner wall at the sealing points. Furthermore, swashplate compressors have already been used but these have the disadvantage that high frictional losses occur therein and this also leads to poor efficiency.
All rotary piston working machines operating by the displacement principle can also be operated as engines. It is for example known to cause disc compressors to operate as disc motors (e.g. in pneumatic tools as drive motors). However, the disadvantages which such machines have as working machines are still present in them as engines or prime movers. Moreover, such engines have a very high consumption of working medium and for this reason also poor efficiency.
Finally, known piston machines have poor size/power ratios.